Support sub mjs module (close #691)

Author: ije

server/build_helpers.go

@@ -219,7 +219,8 @@ func (task *BuildTask) analyze(forceCjsOnly bool) (esm *ESMBuild, npm NpmPackage
 					npm.Types = pkg.Submodule + ".d.ts"
 				}
 			} else {
-				if npm.Type == "module" || npm.Module != "" {
+				asMjs := path.Join(wd, "node_modules", npm.Name, pkg.Submodule+".mjs")
+				if npm.Type == "module" || npm.Module != "" || fileExists(asMjs) {
 					// follow main module type
 					npm.Module = pkg.Submodule
 				} else {

test/issue-691/issue-691.test.ts

@@ -0,0 +1,7 @@
+import { assertEquals } from "https://deno.land/std@0.180.0/testing/asserts.ts";
+
+import extractFiles from "http://localhost:8080/extract-files@12.0.0/extractFiles.mjs";
+
+Deno.test("issue #691", () => {
+  assertEquals(typeof extractFiles, "function");
+});